1. Field of the Invention
The present invention relates to a rotary joint which is applied to a stationary siphon for discharging drain which is generated from a roll of a drier of a machine such as a paper machine and by the condensation of heating steam which has been introduced into the interior of the drier and used in heating the roll.
2. Description of the Prior Art
Such a conventional rotary joint for a stationary siphon will be described with reference to FIG. 3, wherein reference number 20 designates a drier roll of a paper machine. A tubular member 21 having a portion which is shaped so as to form part of a sphere is secured to an axial end of the drier roll 20. The tubular member 21 has at its central location a protrusion forming part of a sphere. The tubular member 21 is also provided on its outer periphery with a plurality of openings 22. At one end of this tubular member 21, another tubular member 23 having an end face shaped so as to form part of a sphere is mounted in such a manner that the second tubular member 23 is, by virtue of the provision of a key 24, slidable on the first tubular member 21 and at the same time rotatable together with the roll 20. A main body 25 is provided in such a manner that it covers the tubular member 21. This main body 25 is supported by a shaft 27 mounted to a bracket 26 fixed to a frame, not shown. More specifically, the shaft 27 is loosely fit into holes formed in protrusions on the upper side of the main body 25, with clearances 33 being provided between the inner surface of these holes and the outer surface of shaft 27. On the lower side of the main body 25, an opening 28 is provided. Carbons 29 are interposed between the inner wall of the main body 25 and the respective tubular members 21 and 23. The tubular member 23 is constantly urged toward one of the carbons 29 by a spring 30. A siphon line 31 is fixed to the outer end of the main body 25, and extends at one end thereof approximately to the inner wall of the drier roll 20, with a clearance 32 being provided therebetween. With this arrangement, steam is supplied from the opening 28 to the interior of the drier roll 20 through the openings 22 of the tubular member 21, and drain which is produced by the condensation of the steam is discharged to the outside through the siphon line 31.
In the conventional device, the siphon line 31 is fixed to the main body 25, while this main body 25 is provided with a certain play which serves to seal steam between the main body 25 and the tubular members and also to allow any vibration due to rotational movement of the tubular members together with the drier roll 20. Because of such arrangement, the position of the siphon line 31 will be varied, making it difficult to maintain an optimum clearance 32 between the end of the line 31 and the inner wall of the drier roll 20. This will greatly influence the drain-discharging performance of the siphon line 31. In addition, the structure in which the siphon line 31 is cantilevered by the main body 25 so as to extend through a long distance fails to provide a firm mounting of the line 31. Particularly when the roll rotates at a high speed, the mounting may be proken by fatigue due to the resistance of the drain. On the other hand, if the diameter of the siphon line 31 is increased in order to improve the strength of the mounting, this may lead to the problem that a one-sided load is applied to the main body, thus impairing its sealing performance.